This disclosure relates generally to methods for increasing the mean particle size of a 2-hydrocarbyl-3,3-bis(hydroxyaryl)phthalimidine.
The compounds 2-hydrocarbyl-3,3-bis(hydroxyaryl)phthalimidine (hereinafter abbreviated as “HHP”) can be used as monomers for producing polymers such as polycarbonates, which are used in high temperature applications. The HHPs are generally prepared by the reaction of a hydrocarbyl amine compound with a phenolphthalein compound in the presence of an acid catalyst, which is then isolated. The isolated product is usually in the form of a fine powder having a mean particle size of less than 2 microns.
The small particle size (i.e., average particles size less than 2 microns) can cause problems during the preparation of polymers and/or copolymers from the HHPs. Among these problems is that these small particles generate airborne dust, which can cause environmental, health and safety issues, such as the risk of dust explosion in an area where the HHP is stored or handled, such as in a chemical plant environment. Another problem is that the fine nature of the particles causes a “slug flow” behavior during operations such as charging the HHP powder into a polymerization reactor, which in turn may lead to an erratic reaction, or to a reaction that is difficult to control. Further, the “slug flow” behavior also causes problems during general transfer of the fine powder from one container to another, particularly on a large scale, such as in a plant environment.
Therefore, there is a need for methods that produce HHP at an average particles size greater than 5 microns. Furthermore, it would be desirable to develop methods whereby the tap density of the HHP can be increased in addition to increasing the mean particle size.